The present invention relates to a lip type seal which seals the circumference of a rotary shaft of various sorts of equipments.
As shaft seal technology using a lip type seal, have a structure as shown in FIG. 4 is conventionally known.
In FIG. 4, reference numeral 100 designates a housing of a shaft hole part of an equipment. Numeral 200 designates a lip type seal which is installed to a seal installation part 101 formed on an inner circumferential surface of the housing 100, and seals the circumference of a rotary shaft 102.
In the lip type seal 200, on an inner circumference of an outer ring part 201 with a packing 201a and a metal ring 201b fixed integrally, a seal main body 202 constituted by an annular sheet made of a synthetic resin such as a fluorine resin and a rear surface support plate 203 constituted by an annular metal plate disposed on the rear side of the seal main body 202 are fixed by caulking of the metal ring 201b. The outer ring part 201 is tightly fitted to the inner circumferential surface 101a of the seal installation part 101 in the housing 100 by the packing 201a. An inner circumferential surface of a seal lip 202a formed on the inner circumferential surface of the seal main body 202 and extending to the side of the sealed space A is sealably brought into slidable contact with the outer circumferential surface of the rotary shaft 102. Therefore, a fluid as a seal object within a sealed space A is prevented from leaking to the side of an atmosphere B outside the equipment.
In the above-mentioned conventional lip type seal, the rear surface support plate 203 restricts deformation of the seal main body 202 to the side of the atmosphere B due to pressure of the fluid as the seal object within the sealed space A. However, considering the vibration of the rotary shaft 102 in the diameter direction and an assembling error such that the rotary shaft 102 is inserted in the housing 100 in eccentric state, the rear surface support plate 203 is formed in such a manner as the inner diameter is larger than the outer diameter of the rotary shaft 102 to some extent. Therefore if the significantly high pressure is produced within the sealed space A, the rear surface of an inner circumference bent part 202b of the seal main body 202 enters a gap G between the inner diameter of the rear surface support plate 203 and the rotary shaft 102. In some case, breakage is produced from the entering portion and the sealing performance may be deteriorated. Particularly, in such a case that the housing 100 and the rotary shaft 102 are eccentric to each other, the gap G becomes large in part in the circumferential direction. Therefore, in this part, the above-mentioned entering of the seal main body 202 is liable to occur.
An object of the present invention is to provide a lip type seal which is excellent in pressure durability, where entering of a seal main body between a rear surface support plate and a rotary shaft due to pressure of a sealed space is prevented.
A lip type seal according to an embodiment of the present invention is provided with an outer ring part which is tightly fitted to a seal installation part of an inner circumference of a housing of an equipment, a seal main body which is fixed to the outer ring part and whose inner circumferential part extending in a bent state to the side of a sealed space is sealably brought into slidable contact with an outer circumferential surface of a rotary shaft inserted in the housing, a rear surface support plate which is arranged on the rear side of the seal main body and whose outer circumferential part together with the seal main body is fixed to the outer ring part, and a movable support plate which is engaged movably in a radial direction between the seal main body and the rear surface support plate and whose inner diameter is clearance fitted to the outer circumferential surface of the rotary shaft. The seal main body is supported through the movable support plate by the rear surface support plate.
In addition, xe2x80x9cfront surfacexe2x80x9d in the present specification means a surface facing the sealed space side, xe2x80x9crear surfacexe2x80x9d means a surface facing the opposite side of the sealed space, xe2x80x9cfront surface sidexe2x80x9d means the sealed space side, and xe2x80x9crear surface sidexe2x80x9d means the opposite side of the sealed space.